The present invention relates to a jointing compound or plaster for construction elements, particularly paper-faced plasterboards, and to a method of producing a work such as a partition, a wall covering or a ceiling.
It is well known to use plasterboards for producing partitions, coverings for vertical or inclined elements, or for producing ceilings, whether suspended or not.
These boards generally consist of a core, essentially made of plaster, covered on each of its sides with a sheet, which serves both as reinforcement, and as facing and which may consist of paperboard or of mineral fibres.
The subject matter of the international application published under number WO-A-9702395 is a method of constructing finishings, in which plasterboards are joined together with a first plaster and the joints between the boards are finished off with a complementary plaster having the following composition:                50 to 85% of a mineral filler;        1 to 20% of an organic binder dispersible in an aqueous phase;        0.2 to 5% of a hydrophobic agent;        1 to 15% of a workability agent (water-retaining agent/thickener);        0.1 to 2% of a slip agent;        1 to 12% of a complementary slip agent;        0.1 to 5% of a dispersant;        0.001 to 0.015% of a pigment;        0.1 to 0.3% of a biocide;        0.1 to 0.3% of an antifoam agent; and        water.        
The colour of this plaster is matched as best as possible to that of the facing paper.
However, such a plaster is a finishing plaster, which means that it cannot be used for filling the space between two boards, especially because it does not allow good bonding and adhesion of the jointing tape. It is therefore necessary to have two plasters: a first plaster, called filling plaster, used to fill the space between two boards, and a second plaster, called finishing plaster, which finishes off the junction between the two boards.
Furthermore, such a plaster has too great a shrinkage after hardening. The colour of the filling plaster is of little matter as it will be covered with the finishing plaster. On the other hand, it must, after drying, have a negligible shrinkage as it is applied with a significant thickness.
However, the colour of the finishing plaster is important as it must be as close as possible to that of the facing of the plasterboard. But it is not necessary for the shrinkage of the finishing plaster after drying to be very low, since this plaster is applied only with a small thickness. The aforementioned application WO-A-9702395 therefore does not address the problem of shrinkage after drying, since this does not matter for the application as a finishing plaster.
It would therefore be beneficial to have a plaster, which could serve both as filling plaster and as finishing plaster. Such a plaster would therefore have to have one or more, preferably all, of the following properties:                good adhesion to the paper constituting the facing of the plaster board;        good bonding and good adhesion of the jointing tape;        a colour identical to that of the facing paper;        a negligible shrinkage after drying (for example, less than 20% as determined by the ring test);        water absorption as close as possible to that of the facing paper, so as to avoid having to use a primer coat before wallpapering or painting;        moderate adhesion of the paper constituting the wallpaper, so as to make it possible for it to be stripped off subsequently one or more times;        easy paintability.        
The Applicant has therefore carried out extensive research for the purpose of developing such a plaster.
It has now succeeded in doing so and consequently proposes a plaster having the following composition: in percentages by weight with respect to the total weight of plaster:                50 to 85% of a mineral filler;        1 to 20% of an organic binder dispersible in an aqueous phase;        1 to 15% of a silicate-based agent;        0.2 to 5% of a hydrophobic agent which is a silicone derivative;        0.05 to 5% of polyvinyl alcohol; and        water to make up to 100%.        
A second subject of the present invention is a method of preparing the plaster, in which the constituents of the plaster are mixed in any order.
A third subject of the present invention is a method of producing a work, comprising the juxtaposition of construction elements, the filling of the space between the construction elements by means of a filling plaster, the laying of a tape and the covering of the tape by means of a finishing plaster and is characterized in that the same plaster is used as filling plaster and as finishing plaster.
Further characteristics and advantages of the invention will now be described in detail in the description, which follows.